This application is concerned with combining ultrastructural and electrophysiological techniques in the study of the neural interactions in the mammalian retina. It consists of three parts: i) We want to record from photoreceptors, horizontal and bipolar cells in slices and cell clumps isolated from the rabbit retina and to analyze their connections with the electron microscope. Purpose of these experiments is to understand the physiology of the various types of bipolar cells and the mechanisms underlying their response properties. ii) We want to record from the neurons of the macaque monkey retina maintained in a superfused eyecup preparation and identify them by intracellular injection of visible markers. Purpose of these experiments is to investigate the functional connectivity of a retina very similar to the human one. iii) By combining rapid freezing at 4 degree K , freeze-fracturing, ultrastructural tracer techniques and electrophysiology, we wish to analyze the mechanism of transmitter release and synaptic vesicle membrane recycling in solitary photoreceptor cells from the rabbit retina. Long-term objective of this application is to discover the mechanisms by which the retina processes visual information. This sort of studies are fundamental to the understanding and rational treatment of the disorders of the retina and nervous system in general.